Examples of such a device include a communication hub for a power meter used in a smart meter system. In the smart meter system, reading data of the power meter needs to be transmitted to a server on the network (for example, an electric power company). For this reason, attachment of a communication hub including a communication function with the network, to a power meter has been reviewed. Since a power meter is often installed outdoors, the communication hub attached to the meter may not include the power supply and may be operated with the power of the power meter. A terminal supplying a drive voltage from the power meter to the communication hub is provided at a connector of the power meter and the communication hub. If the communication hub attached to the power meter is detachable, the communication hub may be removed from the power meter by mischief. Alternatively, even if the communication hub is firmly attached to the power meter without considering the removal, the communication hub may be forcibly removed from the power meter for the purpose of falsification or the like. For this reason, removal of the communication hub from the power meter is desired to be detected. In addition, since the communication hub is required to be operated at any time, shutdown of power supply from the power meter caused by a power failure also needs to be detected.